1. Field of the Invention
The invention relates to a thin film magnetic head which performs magnetic recording operation employing, for example, a vertical recording system, and a method of manufacturing a thin film magnetic head.
2. Description of the Related Art
Recently, a hard disk drive which records information on a hard disk, for example, has been in common use as an information recording apparatus. In the field of development of the hard disk drive, an improvement in performance of a thin film magnetic head is sought in accordance with an increase in a surface recording density of the hard disk. As recording systems of the thin film magnetic head, known are, for example, a longitudinal recording system which involves matching the direction of a signal magnetic field to the in-surface direction of the hard disk (i.e., the longitudinal direction thereof), and a vertical recording system which involves matching the direction of the signal magnetic field to the direction perpendicular to a surface of the hard disk. Although the longitudinal recording system is widely used at present, the vertical recording system instead of the longitudinal recording system is likely to be regarded as promising in the future, considering market trends incident to an increase in the surface recording density. The reason is that the vertical recording system has not only the capability of ensuring a high linear recording density but also the advantage that a recording medium having information recorded thereon is resistant to thermal fluctuation.
As recording systems employing the vertical recording system, there have been proposed, for example, a system which involves recording information on a hard disk having a principal part having a single-layer film structure by using a head having two magnetic poles facing each other with a gap in between at one end and magnetically coupled to each other at the other end (i.e., a ring-type head), and a system which involves recording information on a hard disk having a principal part having a two-layer film structure by using a head located perpendicularly to the hard disk (i.e., a head of single magnetic pole type). Of these systems, a combination of the single magnetic pole type head and the hard disk having the two-layer film structure receives attention as an approach having the possibility of achieving an improvement in performance of the thin film magnetic head in that the combination is remarkably superior in resistance to thermal fluctuation.
Incidentally, an improvement in recording performance of a thin film magnetic head of vertical recording type requires, for example, prevention of the effect of a malfunction generally called “side erase”. The side erase refers to the phenomenon that the recording of information on a track which is a target of recording on the hard disk (hereinafter referred to as “a target track”) causes the information to unintentionally overwrite existing information recorded on a track adjacent to the target track (hereinafter referred to as “an adjacent track”).
The side erase is mainly caused by skew. The skew refers to the phenomenon that the movement of a suspension (that is, a leaf spring made of stainless, which supports a slider) in a track direction during recording operation of the hard disk drive causes the single magnetic pole type head to deviate from the direction of rotation of the hard disk. The occurrence of the skew causes generation of an undesired vertical magnetic field according to a magnetic flux concentrating at a location, other than an intended recording location corresponding to the target track in the single magnetic pole type head. Thus, the undesired vertical magnetic field causes information to overwrite information recorded on the adjacent track. To prevent an adverse effect resulting from the side erase, the single magnetic pole type head can be therefore configured, for example so as to reduce the amount of undesired vertical magnetic field generation, which induces the side erase.
Some suggestions have been already made as to the configuration of a thin film magnetic head designed in consideration of the above-mentioned respect. For example, the technique of partly removing a lower portion of a uniform-width end portion of a single magnetic pole type head, thus reducing the area of an end surface of the end portion, and thereby reducing the amount of undesired vertical magnetic field generation is described at page 67 in the Feb. 12, 2001 issue (No. 789) of NIKKEI ELECTRONICS.
However, this type of single magnetic pole type head has two main problems.
Firstly, the reduction of the area of the end surface of the single magnetic pole type head allows obtaining an advantage in the aspect of the prevention of the adverse effect resulting from the side erase (e.g., degradation in an output signal, etc.), whereas a decrease in the area of the end surface causes a decrease in the amount of magnetic flux for use in recording emitted from the single magnetic pole type head, and this causes a decrease in vertical magnetic field strength and thus causes deterioration in overwrite characteristics which are one of important factors that determine the recording performance of the thin film magnetic head. The overwrite characteristics refer to the characteristics of overwriting information recorded on the hard disk with new information.
Secondly, it is possible that the formation of the single magnetic pole type head having the characteristic configuration having the end portion having the lower portion partly removed requires a partial removal of the lower portion of the end portion on the side of an air bearing surface using an etching technique such as FIB (focused ion beam) process having low manufacturability. Therefore, the technique is inferior in manufacturability, and etching may do damage to the single magnetic pole type head or the periphery thereof.